The present invention relates to a control circuit for predominantly inductive loads, in particular, electroinjectors forming part of an internal combustion engine supply system.
For controlling internal combustion engine injectors, the supply current to the injectors must present a pattern comprising, in general, a rapidly increasing portion, a portion increasing more slowly, a portion oscillating about a mean value, and a rapidly decreasing portion. The circuits currently employed for achieving such a pattern substantially comprise a low-voltage supply source and a reactive circuit consisting of an inductor and capacitor for storing the energy required for producing a rapid current pulse in the load. For this purpose, the inductor is charged to a given current and then connected to the capacitor, so as to form a resonant circuit and transfer energy from the inductor to the capacitor, which is thus charged for subsequently supplying the load (injector actuator) with the required current pulse.
A major drawback of the above known circuit is that, for achieving the high currents required, large-size components such as cup-shaped or toroidal cores are used as inductors on the reactive circuit, thus increasing the size and cost of the overall circuit.
The above problem is further compounded by the fact that, for protecting the control elements of the actuators, each actuator presents a so-called "snubber" circuit comprising a capacitor and resistor connected parallel to the actuator, and which provide for absorbing and dissipating the energy of the recirculating current of the actuator. Such capacitors further increase the overall size of the circuit.